1. Field of the Invention
The present invention is related to an apparatus and a method of reducing electromagnetic noise on the input and outputs of an electronic component; and in particular, to an apparatus and a method of reducing electromagnetic noise on the input and output of an electronic component contained in an automobile.
2. Background Art
The inclusion of electronic components in motor vehicles tracks the development and improvement of such devices. Since the development of the first automobiles, there has been a continuing trend to replace mechanical devices with electronic devices which operate in a more sophisticated manner. Such devices include, for example, braking systems, engine control microprocessors, and the like. Moreover, new technologies have been integrated into automobiles as such technologies have become available. Examples of such technologies include entertainments systems (radio, CD players), communication systems (cell phones), navigation systems, environmental control systems, and the like.
Electronic components are potential noise sources if onboard devices are performing high-speed switching. Similarly, nearby sources pass noise to the electronic components through input/output ports, which disturb the component. Moreover, part of the undesired energy may be re-distributed to other ports of the electronic components. Hybrid electric vehicles (HEVs) and electric vehicles, in particular, are replete with electronic devices and components. Such components include both sophisticated integrated circuit based devices and well a relatively large passive-component based system. In addition to the components which may be found in an internal combustion vehicle, HEVs typically include a high voltage battery which is used to operate a motor/generator assembly which provides torque to the wheels of the vehicle. Operation of an HEV or an electric vehicle requires conditioning of the electrical signal between the high voltage battery and the electric motor to provide compatibility between the inputs and outputs of the various components within the HEV. Such conditioning components include, for example, converters, inverters, rectifiers, and frequency changers. Inverters are used to converts DC voltages to AC voltages, rectifiers convert AC voltages to DC voltages, and frequency changers matches the input AC power to the required AC output.
To stop noise propagation, filters are implemented near the input/output ports of electronic components in order to attenuate electromagnetic noise of the components inputs or outputs. Such filters normally have low-pass characteristics with shunt capacitors between signal traces and a reference plane (normally it's the ground plane). Unfortunately, in many cases the reference planes are noisy thereby cause the noise to find a path from the noisy reference plane through the shunt capacitors to the signal lines. In other words, these shunt capacitors may introduce more noise to the signal lines than initially present. To address this problem, the reference plane noise level must be reduced which is not easy or nearly impossible. Another approach is to identify a quiet area as a new reference plane. To keep this new zone quiet, major noise currents must be isolated from this area with enough isolation between this area and the noisy regions to produce acceptable levels of noise on the signal lines.
Accordingly, there exists a need for improved strategies for reducing the affect of electromagnetic interference on the electronic components of a vehicle and in particular on the electronic components of a hybrid electric vehicle.